Apparatus for testing breaker mechanisms



Nov. 30, 1943. A. H. HANSON APPARATUS FOR TESTING BREAKER MECHANISMSFiled Sept. 6, 1941 A llllll AAAAAAAIA "17"" lya Ill.

INVENTOR. 4112 ED him ON ATTO NEYS Patented Nov. 30, 1943 APPARATUS FOR-TESTING BREAKER MECHANISMS Alfred B. Hanson, Garrison, N. Y., assignorto Patterson 0. Stewart, New York, N. Y.

Application September 6, 1941, Serial No. 409,766

8 Claims. (Cl. 177-311) My invention relates to a new and improveddevice for testing and analyzing the operation of the distributorbreaker-point mechanism of the ignition system of an internal combustionengine.

One of the main objects of my invention is to provide a new and improvedinstrument for accurately indicating the cam angle of the breakerpointsof the distributor, while the engine is operating, without removing thedistributor and without altering the wiring of the ignition system.

Another object of my invention is to indicate the presence of worndistributor parts which are associated with the function of thebreakerpoints of the distributor, such as defective breaker-springs,breaker-point resistance, defective wiring and the like.

Another object of my invention is to provide an indicator which can beused in synchronizing the cam angle of dual breaker-points.

Another object of my invention is to provide an electric meterincombination with a circuit so that the reading of the meter isunaffected by the reactance of the primary coil of the ignition system.The meter circuit is substantially non-'- inductive so as to permit thereading of the instantaneous current value which flows through thebreaker-points.

Another object is to provide a circuit to indicate cam angle, by usingan electronic vacuum tube whose filament may be heated by direct currentor alternating current from any source. Said electronic vacuum tube ispreferably a diode, whose cathode is heated by said filament. Thecathode is insulated from the filament. The circuit does not requireanyplate potential.

Other objects of my invention will be stated in the followingdescription and diagrammatic drawing.

Fig. 1 is a diagrammatic view which illustrates the principle of theimproved circuit.

Fig. 2 is a more complete circuit diagram, based on the same principle.1

The invention is illustrated in connection with a conventional batteryignition system for the internal combustion engine of an automobile, inwhich a primary coil is connected to a storage battery throughbreaker-means. However, the invention applies to all ignition systemswhich employ breaker-point mechanism. It therefore is not restricted toan ignition system which has a battery as the source of electric currentand it may be applied, with slight modification, to magnetos andvibrator point dwell tests. Hence, whenever I refer to a storage batteryin the description or claims, I include other suitable sources ofelectric current.

The principle of the invention is based upon the fact that a substantialcurrent flow exists between the plate and the cathode of an electronicdiode, even when no positive potential is applied to the plate. Uponconnecting a low resistance milliammeter between the plate and thecathode, it is found that there is a. space charge current of between300-1000 microamperes, even when no positive potential is applied to theplate. This space charge current is purely electronic and it does notflow from the source of current of the filament which heats the cathode,because said heating filament is insulated from the cathode.

Likewise this space charge current continues to flow as long as thecathode remains heated to the proper temperature, and even after theheating filament has been disconnected from its source of current. Ineifect, the diode generates a constant and individual difierence ofpotential between the cathode and the plate, which is inde-- pendent ofthe source of current to which the heating filament is connected. Thecathode may, therefore, be heated in any suitable manner, as by means ofa direct current from an ignition battery, from any suitable source ofalternating current or in any other manner.

Fig. 1 shows the storage battery I of any ignition system for automobileengines or the like. This battery has a positive pole P and a negativepole N. The positive pole P is connected by the wire l5 to the pivotpoint 8a of the breaker-arm 8b, which is oscillated in the usual mannerby the conventional cam (not shown). Said turnable breaker-arm 8b hasthe usual contact point 8. The arm 8b is biased in the usual manner bythe conventional spring, to produce contact between the movablebreakerpoint 8, and the stationary breaker-point 1. This stationarybreaker-point l is adjusted by conventional means. The usual ignitioncon- 6 denser 9 is connected in shunt across the points resistance l4,whose value may be 100 ohms.

Whenever specific figures are stated herein, this is only as an exampleand the invention is not limited thereto. The other end of the resistance I4 is connected to the point A, which is connected to the cathode46 of the diode. The heating filament 38 of the diode is of any suitabletype and it is insulated in the usual manner from the cathode 46 of thediode and also irom the plate 41 of the diode. The heating filament 38of the diode may be connected to the circuit at the points 2b and 20b,in order to draw heating current from the battery I. As previouslystated, the filament 38 may be heated in any suitable manner. The plate41 of the diode is connected to one terminal of the milliammeter 50. Theother terminal of the milliammeter 50 is connected through theadjustable resistance 52 to the point B. The points A and B areconmilliammeter 50, in order to make full-scale adjustment in the usualmanner.

The operation of the circuit illustrated in the diagram is as follows:

When the breaker-points I and 3 are closed, there is substantially no IRdrop through the direct circuit between the points Md and It, becausethe resistance of'the points I and 8 is substantially zero and theprimary coil I2 then supplies practially all of the impedance of thecircuit. Current will flow through the primary coil I2, when thebreaker-points are closed.

Due to the electronic effect of the diode which has been previouslymentioned, said diode maintains the point B at a higher potential thanthe point A. This difference of potential is much less than the voltageof the storage battery I, which is ordinarily either 6 volts or 12 voltsand even more. When the breaker points are closed, substantially nobattery current will flow from point Ma to 2b, and through resistancesI4 and I9 to point I5, because of the negligible resistance of theclosed breaker-points. The IR drop of the battery current through theresistance I9 will be negligible when the breaker-points are closed, sothat the difference of potential of point A above that of point B whichis produced by the battery current will be negligible and much less thanthe difference of potential of point B over point A, which is producedby the diode. Hence current will flow from the plate 41 through themilliammeter 50 to the cathode 46, during each interval in which thebreaker-points are closed.

Likewise, the resistances I4 and I9 are connected in parallel withrespect to the electronic current of the diode when the breaker-pointsare closed, because said electronic current can flow from the point B tothe point I6, through the closed breaker-points to the point MA,

through the wire 2| to the point 2b, and through the resistance I4 tothe point A.

When the resistances I4 and I9 are thus con- This voltage drop is atleast equal to and it is preferably greater than the electronicpotential of the diode. Hence the electronic current will be immediatelyinterrupted when the breakerpoints I and 8 are open, because the cathode46 is then at a higher potential than the plate 41.

The meter 50 will therefore indicate the total value of the currentpulses which are sent through said meter, during the periods of timewhen the breaker-points are closed. The meter 5b is calibrated by meansof the adjustable resistance 52, by closing the circuit of said meter 50to secure full continuous current, the resistance 52 being adjusted soas to secure full-scale reading.

Therefore, the reading of the scale under test conditions, indicates thesummation of a series of intermittent current pulses, which arecoincident with the current pulses which are passed by the batterythrough the primary coil I2.

The meter 50 therefore measures the instantaneous value of the currentwhich flows through the breaker-points and the reading of the scale ofthe meter 50 will exactly show the percentage of time that the batterycurrent flows through the intermittently interrupted circuit of theprimary coil I2. ,For example, if the reading of the meter I0 drops toone-half the calibrating reading, under test or operating conditions,this will show that current is flowing through the meter 50 and throughthe breaker-points, only one-half of the total time.

When the breaker-points I and 8 are opened,

the inductance of the primary coil I2 tends to maintain the flow ofcurrent through said coil I2, in the direction of the arrow R. Thisdirection is the same as the direction of the current through said coilI2, when the breaker-points are closed. However, this reactance currentcannot flow through the meter 50 because the resultant voltage makes thepoint A of higher potential than the point B, so that the cathode 46 hasa higher potential than the plate 51. The meter 50 is thus automaticallydisconnected from the circuit of the primary coil I2, during theintervals in which the breaker-points i and 8 are separated.

In addition, when the breaker-points I and 8 are separated, thecondenser 9 is charged to saturation by the self-induced voltage of thepri-' mary coil I2. The condenser 9 will discharge through the battery Iand through the resistances I4 and 9 and through the primary coil I2.However, as the direction of this discharge current maintains the pointA and the cathode 46 of higher potential than the point B and the plate41, this current will not pass through the milliammeter 50. Although thereactance efiect of the primary coil I2 produces successive alternationsof current flow, which would tend to make the point B and the plate 41of higher potential than the point A and the cathode 46, this disturbingfactor is not of sufficient magnitude to affeet the result which issecured by the steady flow of direct current from the battery I, throughthe resistance I9. Resistances I4 and I9 also decidedly dampen theoscillations of the condenser 9.

The invention is especially useful in accurately testing the operationof the breaker-points 1 and 8 during the actual running of the engine ofthe automobile or the like. If the points I and 8 are set by a thicknessgauge or synchrograph, the setting of the breaker-points I and 8 may bechanged during the operation of the engine, due to thrust conditions.

According to my invention, the operator can thus measure the cam angleunder actual operating conditions, so as to compensate for the eflectsoi centrifugal force and of inherent thrust conditions. On the contrary,if the breaker-points are adjusted by a synchrograph, the cam anglesetting may chang under operating conditions.

Tests have shown that if the primary coil I2 is replaced by anon-inductive resistance, the reading of the meter 50 remainssubstantially the same, if the resistance of the substituted coil isequal to the pure resistance of the primary coil l2. This shows that thereactance of the primary coil has no effect upon the reading of themeter 58, under operating conditions. It current is supplied to theheating filament 38 from any suitable source of alternating current orby a battery which is external to the ignition system, the full-scalesetting of the meter 50 is unaffected by the voltage of the ignitionbattery I of the automobile; Therefore one setting of the meter 50 canbe made prior to the actual testing, by adjusting the resistance 52, andthis calibration remains constant throughout the test, independently ofthe voltage of the battery I, the action of the generator of theignitionsystem, etc.

If the heating current of the filament 38 is sup. plied by the battery Iof the ignition system, the temperature of the filament ,38 will varywith the action of the generator of the ignition system, thus affectingthe full-scale setting or calibration of the meter 58. It is possible,but not desirable, to include a ballast resistance in the filamentcircuit so that it is unnecessary to make more than a single initialadjustment of the calibrating resistance 52. However, if the batterycurrent is used for heating the filament 38, the simplest method is tomake an accurate adjustment ofthe resistance 52, prior to making eachtest of cam angle or the degrees of dwell.

In the circuit of Fig. 2, the positive pole P of the battery I isgrounded at G through the wire 2, since it is conventional toground oneterminal of the ignition battery of an automobile. In the majority ofcases, the positive pole is grounded, but in some cases the negativepole N may be grounded, so that I have provided a polarity switch S. Thesetting of this polarity switch S, which is shown in Fig. 2, correspondsto the grounding of the positive pole P of the battery l.

The positive pole' P is connected through the wire- 1a to the point 6,which is connected by the con- P is connected by the wire 2 totheterminal 33 of a switch which has a movable, switch arm 35, which isturnably or otherwise 'movably connected to the terminal 34. If thebattery lis asixvolt battery, the switcharm 35 is moved by the operatorto connect the terminals 33 sneer; so

as to cut out the resistance 38, which connects the terminal 34 to thepoint 37. If the battery is a twelve-volt battery, the switch arm 35 ismoved to a circuit-opening -position so that the heating current of thefilament 38 passes through the. resistance 36, when the switch arm '35is .moved to the circuit-opening position. The negative pole N is alsoconnected by a wire 50 to the terminal 4! of a switch which has anotherterminal 39;and a manually operable switch arm' '49;

Whengthe filament 38 is to be heated by the battery current, the switcharm 48 is moved to connect the terminals 4| and 39.

If the filament 38 is to be heated by an alternating current, the switcharm is moved by the operator to connect the terminals 39 and 42. Thesecondary .coil 44 of a transformer has one end thereof connected to theterminal 42, and the other end thereof is grounded at 45. This secondarycoil 44 is inductively coupled to the primary coil 43 of a transformer,which is connected to any suitable source of alternating current. Whenthe filament 38 is heated by alternating current, the switch arm 35 ismoved to connect the terminals 33 and 34, so as to round one end of thefilament 38 at G. The heating transformer is a step-down transformer, ifordinary commercial alternating current issupplied to the primary coil43. The point 3a of the wire 3 is connected to the movable breaker-arm8b which is pivotally mounted at 8a in the usual manner. Theconventional spring 80 biases the arm 8b to the position in which thepoints I and 8 will contact with each other.

Fig. 2 also illustrates the conventional cam 8d which rapidly oscillatesthe arm 8b, so as to make and break the circuit. A stationary butadjust,- able point I is connected to the point I i of the wire 1, bymeans of the wire H). The point VII of Fig. 2 corresponds to the point|4a of Fig. 1. The points II and A are connected by the resistance [4,which preferably has a value of 100 ohms, as in the preceding example.The points A and B are connected by a resistance l9, which alsopreferably has a value of 25 ohms, as in the preceding example. Thepoint B is connectedto the terminal l'la and said terminal l'la can beconnected either to the test terminal 13a, or to the set terminal [5a,by means of the manually operated switch arm H3. The terminals Ila andMia are connected when the ignition system of the engine is being testedunder actual operating conditions. The point'A is connected to theterminal 29 of the'polarity switch S by the'wire 3i. Thepoint B. isconnected to the terminal 30 of the polarity switch S by the wire 32.The terminals 29 and 23 are connected by the blade 21 of the movable armof the polarity switch, and the terminals 38 and 24 are connected by theblade 28 of said movable arm, when said movable arm is in the positionofFig. 2. The blades 21 and 28 are respectively pivotally mounted at theterminals 29 and 30, in the conventional manner. The terminal 23 isconnected to the terminal 22 by the wire 25 and the terminal 24 isconnected to the terminal 21a by the wire 26. The cathode -.46 isconnected to the terminal 22-by th wire 22a. In the circuit of Fig. 2,the diode 39 is provided with two plates 41 and 48, as in a full-waverectifier, and these plates are connected toLthe terminal 49 of themilliammeter 50. The'terminal 5| of the milliammeter 53 is connectedthrough the adjustable resistance 52 to-the terminal 2la.

7 Assuming that the, switch arm l8 connects the,

terminals 16a and Ho, it' is clear that the 015- eration of the circuitof- Fig. .2. is substantially the same as the circuit of Fig. 1. Whenthe breaker-points 7 and Bare closed, current' will 1 flow from thepositive pole P through the wire la to the point ll, through the wire l0to the fixed breaker-point I, through the breaker-point Band thebreaker-arm 8b to the terminal 8a; and t0 the point 3a of thewireisothatthe circuit is closed through the primary coil l2.

Current will then also flow from the point point a and back through thewire 3 and the primary coil l2 to the negative pole N.

However, for the reasons previously explained, the resistances l4 and I9are then connected in shunt with respect to the electroniccurrent of thediode 39. Current will therefore flow from the plates 41 and 48 throughthe milliammeter 50, through the resistance 52 to the terminal 2la,through the wire 26 to the terminal 24, through the blade 28 to theterminal 30, through the wire 32 to the point B, through the resistancel9 to the point A, through the wire 3| to the terminal 29, through thearm 21 to the terminal 23, through the wire 25 to the terminal 22, andthrough the wire 22a to the cathode 46.

When the breaker-points 'l and 8 are open, the battery current will flowfrom the positive pole P through the resistances l4 and It (now arrangedin series) and through the switch arm l8 to the negative pole N. Thefiow of the electronic current of the diode 39 will therefore beinterrupted during the successive intervals in which the breaker-pointsare open. The actual' value of the resistance 52 is about 1500 ohms.

In order to set or calibrate the meter 50, the switcharm I8 is moved toconnect the terminals I51; and Ila, while the engine is operated at thetest speed if the battery current is used to heat the filament. If thefilament is heated by a source of alternating current or by an externalbattery, the engine can be run at any speed during the calibration.Referring to Fig. 1, the effeet is the same as though point B weredirectly connected to point Ma, insteadof being connected to point l6.Due to the reasons previously explained, the electronic current of thediode 39 will then flow continuously through the milliammeter 50 whenthe breaker-points are open and when they are closed. The resistance 52is then adjusted in order to secure full-scale reading with saidcontinuous electronic current. This electronic current through the meter50 may vary from about 0-600 microamperes, depending upon thetemperature of the cathode.

The operation of the diode 39 does not depend upon any passage ofcurrent between the filament 38 and the plate or plates of the diode.This can be demonstrated by disconnecting the filament wholly from theheating circuit, because the circuit will then operate in the mannerabove mentioned, as long as the cathode 46 is sufficiently hot to emitelectrons.

The output voltage of the generator of the ignition system of anautomobile varies with the speed of the automobile engine. It istherefore desirable to maintain the speed of the engine constant duringthe test and to reset or recalibrate the meter 50 for each differentspeed of the engine at which the cam angle is to be tested. It is alsodesirable to turn on the lights of the engine during the testing, asthis helps to stabilize the voltage. However, by heating the cathode 46independently of the battery I, many or all of these factors can beeliminated.

According to the improved circuit, the voltage of the source of ignitioncurrent is used to bias the electronic source of current, so that thecurrent of the electronic source is absolutely interrupted when thecircuit of the primary coil is open. The invention is not limited tothis preferred embodiment, because the current from the electronicsource may be discontinued in any manner when the circuit of the primarycoil is open. Likewise, the invention includes a circuit whereby thecurrent of the electronic source through the meter is diminished,instead of being absolutely inter upted, while the circuit of theprimary coil is losed, since absolute interruption is diminution.

Likewise, the invention is not limited to an ignition system in whichthe source of ignition current is" a battery. The function of thebattery and primary coil is to produce a current of sufficient potentialto discharge through the points of the spark plug, and said dischargecurrent may be secured in any suitable manner.

The improved test and calibration circuit of Fig. 2 can be convenientlyembodied in an instrument which includes the resistors 36, l4, IS, thepolarity switch S, the diode 39, meter 50, adjustable resistor52, theswitches which have the arms 35 and 40, and the heating transformer.

The instrument can be used by connecting one end of each of theresistors 36 and I l-to the positive-pole P of the battery, and byconnecting the terminals 33 and 4| of the instrument respectively to thepositive pole P, by connecting the terminal 15a .of the instrument tothe positive pole P, and by connecting the terminal [6a of theinstrument to the negative pole N. The instrument can thus beconveniently applied to or detached fromv the ignition system of aninternal combustion engine.

I have shown a preferred embodiment of my invention, but it is clearthat numerous changes and omissions can be made without departing fromits spirit.

While the use of a pair of resistors l4 and I9 is preferred, theresistance l4 may be omitted, and the resistances of resistors l4 and I9may have any desired relation, instead of having the rethe current fromthe diode, when the breakerpoints are open. When the breaker-points areclosed, the IR drop between points Ma and I6 through the closedbreaker-points is negligible, and hence the IR drop through resistanceI9 will be insuflicient to block the current of the diode.

However, it is preferred to use the two resistances l4 and I9, or tomake the A. C. reactance of element l4 exceed that of element IS, inorder to secure best result.

When the breaker-points are opened, the reactance of the primary coilcan produce a reactance voltage in the order of 300-500 volts, and suchreactance voltage tends to produce a high current flow for a very shortfraction of a second. If the resistance M were omitted, leaving only thelow resistance H), the reactance voltage would be substantiallyshort-circuited, so that the instrument would seriously affect, thenormal operation of the coil. By using a sufliciently high resistance M,the coil l2 functions normally. Instead of being a pure or non-inductiveresistance, the element l4 could be a coil with low direct currentresistance (about 10 ohms) and with suflicient inductance so as to havea higher reactance than the non-inductive resistance l9.

It will be noted that the diode is not connected in parallel to thebattery with the primary coil l2, because no battery current can everflow through the diode.

The meter 50 is preferably a direct-current meter, which will indicatethe current only when the current flows through said meter in a pre-.

predetermined direction. However, I can use any type ofcurrent-measuring device. Likewise, I can use any source of electroniccurrent.

I claim:

1. In combination with the battery and breaker-points of an ignitionsystem which has a primary coil connected in series between thebreaker-points so that the circuit of the primary coil is made andbroken by the contact and separation of said breaker-points, said systemalso having means for successively contacting and separating saidbreaker-points, a shunt circuit which has its ends connected across thebreaker-points so that the full battery current flows through said shuntcircuit when the breaker-points are opened, said shunt circuit includinga resistor, an electronic source of current which has a cathode and aplate and which is adapted to generate current at a predeterminedvoltage when the cathode is heated, said predetermined voltage beingless than the battery voltage and being less than the IR drop of thebattery current through said resistor when the breaker-points areseparated. the resistance of the contacting breaker-points beingsufficiently less than the resistance of said resistor so that the IRdrop oi thebattery current in said resistor is less than saidpredetermined voltage when the breaker-points are in contact, said platebeing connected to one end or said resistor, sai cathode being connectedto the other end of said resistor, the first-mentioned end of saidresistor being of lower potential than the second-mentioned end whenbattery current flows through said resistor.

2. A combination according to claim 1, in which the shunt circuit has asecond resistor which is located anterior to and which has greaterresistance than the first-mentioned resistor.

3, A combination according to claim 1, in which a'source oi heatingelectric current is connected to said electronic source to heat thecathode thereof, said source of heating electric current beingindependent oi the latter.

4. A combination according to claim .1, in which a a source or heatingelectric current is connected to said electronic source to heat thecathode thereof, said source of heating electric current beingindependent oi the latter, said source of heating electric current beinga sourceoi alternatina current.

5. A test instrument for testing a system which has periodidallvseparated breaker-points, which comprises a source of electronic currentwhich has a positive terminal and a negative terminal, said instrumentalso comprising a first resistor and a second resistor and alsocomprising a current-measuring device. the first resistor having greaterresistance than the second resistor, said resistors having respectiveproximate ends which are connected to each other, said resistors alsohaving respective remote ends, means adapted to connect said respectiveremote ends to the circuit which is to be tested and in shunt acrosssaid breaker-points, the positive terminal of said source of electroniccurrent being connected to the remote end of said second resistorthrough said current-measuring device, the negative terminal of saidsource of electronic current being connected to said resistors at theirproximate ends, so that the current of said source of electronic currentis urged to flow in parallel through said resistors when the circuitbetween said remote ends is completed.

6. A test instrument according to claim 5, in which said source ofelectronic current has a cathode and an anode, and means for heating thecathode to electron-emitting temperature by means of alternatingcurrent.

'7. Means for testing a circuit which has asource 01' unidirectionalcurrent and terminals which are alternately contacted and separated soas to successively make and break said current, said means comprising ashunt circuit across aid terminals, said shunt circuit having animpedance, a sub-circuit whose endsare connected to said shunt circuit,said impedanc being located between the ends of said sub-circuit so thatsaid impedance common to said shunt circuit and said sub-circuit, adiode located in said subcircuit, said diode having a heatedelectron-emitting cathode and an anode, said diode being the only source0! current in said sub-circuit, an electric meter located in saidsub-circuit, said diode delivering a unidirectional current whosedirection through said impedance is opposed to the direction 01 thecurrent of the first-mentioned source through said impedance, thevoltage dii'ierence which is impressed by said diode upon said impedancebeing greater than the opposed voltage difference which is impressed bysaid first-mentioned source when said first-mentioned circuit is closed,the voltage difference which is impressed by said diode upon saidimpedance being less than the opposed voltage ditierence which isimpressed by said first-mentioned source when said first mentionedcircuit is open, said diode blocking the passage or current from saidfirst mentioned source through said sub-circuit when the first-mentionedcircuit is open and closed, said meter receiving current only from saiddiode and only when said firstmentioned circuit is closed.

8. Means according to claim 7 in which said shunt circuit has anadditional impedance which is located anterior to said common impedance,the value of said anterior impedance exceeding the value 01' said commonimpedance.

ALFRED H. HANSON.

